The invention is based on a procedure for operating a particle filter that is arranged in the exhaust gas area of a combustion engine and on a device for implementing the procedure.
DE 199 06 287 A1 describes a procedure for operating a particle filter of a combustion engine, which is regenerated if required. Without a conditioning of the particles the particles oxidize at a temperature of about 550° C. The required particle ignition temperature can be achieved with a reagent, for example uncombusted hydrocarbons, which is inserted into the exhaust gas area of the combustion engine, reacts exothermally at the catalytically working surface and therefore increases the exhaust gas temperature upstream in front of the particle filter.
In certain operating conditions of the combustion engine the case may occur that the regeneration runs uncontrollably fast because of the increased oxygen content of the exhaust gas. Due to the strong exothermic oxidization of the particles an inadmissibly high temperature increase in the particle filter may occur. In order to avoid such a condition DE 103 33 441 A1 suggests to influence the particle burning rate with the aid of the exhaust gas lambda. A nominal value for a lambda signal or a nominal value for a change of the lambda signal is predefined, which is compared to the measured exhaust gas lambda. Depending on the deviation between the nominal and the actual value a control signal is provided for a control element, which influences the oxygen concentration in the exhaust gas. An exhaust gas recirculation valve, a throttle valve etc can for example be provided as control element.
DE 101 08 720 A1 also describes a procedure and a device for controlling a combustion engine, which contains a particle filter, which is arranged in the exhaust gas area and which is regularly regenerated. Based on an operating parameter of the combustion engine and/or the particle filter a parameter is determined, which characterizes the intensity of the exothermic reaction in the particle filter during the regeneration. If the intensity parameter exceeds a threshold value, measures are taken for reducing the oxygen concentration in the exhaust gas in order to reduce the particle burning rate.
DE 199 06 287 A1 describes a further procedure for controlling a combustion engine, in whose exhaust gas area a particle filter is arranged. The temperature increase for starting the regeneration of the particle filter is achieved with a reagent, which is inserted into the exhaust gas area of the combustion engine upstream in front of the particle filter. Fuel is provided as reagent, which reacts in the exhaust gas area exothermally, for example on a catalytically working surface of a catalytic converter. The fuel gets into the exhaust gas area by adjusting the fuel injection timing, which causes an incomplete combustion of the fuel.
The insertion of fuel into the exhaust gas area of the combustion engine can be carried out according to DE 10 2004 033 414 A1 alternatively or additionally to the adjustment of the fuel injection timing by at least one fuel after-injection. Provided are at least a first and at least a second fuel after-injection. The first fuel after-injection is a fuel after-injection that is leaned on a main-injection, at which the injected fuel only combusts partially, so that uncombusted fuel gets into the exhaust gas area. The second fuel after-injection is a late fuel after-injection, at which the fuel does not combust anymore and gets mostly into the exhaust gas area.
The load condition of a particle filter can for example be determined according to DE 199 06 287 A1 with the aid of the determination of the difference pressure occurring at the particle filter.
DE 101 18 878 A1 describes a procedure for operating a combustion engine, at which an overrun cut-off is provided in order to save fuel. The overrun cut-off becomes active if the engine speed of the combustion engine lies above an engine speed threshold value and if simultaneously there is no load demand. A cooling off of a catalytic converter that is arranged in the exhaust gas area of the combustion engine is thereby avoided, in that the exhaust gas recirculation rate is increased during the overrun cut-off.